When people feel their needs aren't being met by mainstream political parties, they seek answers in the fringes.
This is frightening and seems to be happening all over the Western world. Personally, I think people are struggling with the social disconnect brought by technology, with the smaller family sizes required by economic and climate conditions, with the simmering dread brought on by climate change, and an increasing rage as the struggling middle and lower classes are inundated with daily news of billionaires engaging in frivolity, waste, and/or crimes against the most vulnerable members of our society. People are becoming cynical and angry. They don't see the future as bright.
In a situation like that, people seek alternatives to the status quo. What could be more attractive than a political view based on returning to old times? They want the return of economic security, stronger family units, more disposable income for leisure, and all the other real or perceived benefits of times past. They think that getting there will require us to embrace the other things we are trying to leave behind - racism, sexism, perhaps even war and genocide in some of the more extreme fringes.
We can see it globally in the left wing too. This is where the terms conservative and progressive really shine as being good descriptors. Conservatives want to go back to the glory days. The more extreme they are, the more willing they are to embrace the worst parts of our past. Progressives/liberals want to move forward. The more extreme they are, the more they are willing to try radical new things that sound like fantasy or science fiction. Progressives are often willing to upend massive social and economic structures to try new things. I find myself in this camp, and sometimes I step outside myself and admit that I have some pretty extreme views. I once told my conservative uncle that I would absolutely be willing to eat my food in pill form, edit my genes so I could live forever, change my brain chemistry so I could be happy all the time. He was shocked and said those things were inhuman and evil.
I don't believe that we can convert people back to the mainstream unless the mainstream starts to meet their needs. Nations with hungry, lonely, and unfulfilled people are probably good breeding grounds for revolution, in my opinion. Unfortunately, revolutions aren't always good. Bad actors often take advantage of instability.